Emergency responders gather in the parking lot of Franklin Regional High School in Murrysville, Pa., where several people were stabbed on April 9. / Keith Srakocic, AP

by Marisol Bello, Oren Dorell and Alicia McElhaney, USA TODAY

by Marisol Bello, Oren Dorell and Alicia McElhaney, USA TODAY

MURRYSVILLE, Pa. - A male sophomore described as "really shy"' went on a slashing and stabbing rampage Wednesday with two kitchen knives at a high school here, injuring at least 20 students and a security guard before he was subdued and handcuffed, police said.

At least 12 people were hospitalized with serious injuries, many with deep puncture wounds to the abdomen, hospital officials said.

Doctors said a 17-year-old male student was in critical condition after being stabbed in his liver, diaphragm and major blood vessels, but that the blade missed his heart and aorta. A second student is also in critical condition, Murrysville Police Chief Thomas Seefeld said.

A security guard was stabbed in the stomach during the ordeal, but was treated and released from the hospital, police and hospital officials confirmed.

The suspect was identified in court documents as Alex Hribal. He was charged as an adult with four counts of attempted homicide and 21 counts of aggravated assault.

Hribal appeared in court Wednesday afternoon, shackled and wearing a hospital gown. Seefeld said the suspect was treated for injuries to his hand.

Police know of no motive for the rampage, did not know about the student and had no warning of the attack, Seefeld said.

The 16-year-old sophomore was tackled by Assistant Principal Sam King and handcuffed by School Resource Officer William "Buzz" Yakshe, he said.

At least a dozen FBI agents arrived at the suspect's home on a quiet cul-de-sac in Murrysville and waited to enter the home late Wednesday.

The house, newer brick-front suburban home with a two-car garage and University of Pittsburgh flag in the front yard, is a half-block from the home of the assistant principal who tackled him and ended the rampage.

Outside a few moments before, Franklin Regional juniors Justin Katonak and Max Kubas, both 17, remarked on how normal the street and the suspect's family had seemed to them until this morning.

Student Matt DeCesare said Hribal was quiet and not widely known. He said most victims did not appear to be linked with him and were simply close by when the attack began.

"I know most of the kids who were injured," he said. "They don't have any connection to him."

DeCesare said some students thought Hribal had been anxious or upset recently, and that he had shouted at a girl who had asked to see his homework Wednesday morning.

At Newlonsburg Presbyterian Church, Pastor Curtis Paul sought to provide support in an evening service.

"We may never know why this happened," he said. "God gives us the gift of freedom, and many times we misuse that freedom.""

He urged worshippers to pray for their community, the injured, their families, and even "for the boy who did it because he too was a child of God."

The attack in a long corridor occurred shortly after 7 a.m., before classes began. Police secured the scene within five minutes after Yakshe's radio call for help, Seefeld said.

When help arrived, police found "the hallway was pretty much in chaos," Seefeld said. "Blood on the floor. We had students running about."

Seefeld said a fire alarm triggered during the incident at Franklin Regional High School prompted students to flee the building, likely keeping down the number of victims.

Sophomore Trinity McCool told USA TODAY that the suspect, after attacking several other people nearby, took a swipe at her and a friend with what looked like a butcher knife.

"I saw his face, the look in his eyes, I was horrified," she said.

Another student, Nate Scimio, blocked the attack, however, by sticking out his arm as the blade came down.

"(Nate) took the stab right in his arm and saved my friend and me," McCool said. "I'm pretty sure it was his instinct. He didn't want anyone to get hurt. He told everybody to run away."

McCool said Scimio also apparently set off the fire alarm that sent students rushing to the exits. Scimio later tweeted a selfie from the hospital showing his right arm in a bandage.

Mia Meixner, a sophomore, told USA TODAY that she was putting her books away near the cafeteria when she heard a commotion and saw the male suspect "stabbing people on top of a freshman."

She said the suspect "just got up and ran away really fast." Meixner identified the suspect, but USA TODAY is withholding his name from publication.

"The freshman stood up, lifted up his shirt and he was gushing blood," Meixner said. "I also saw a senior girl ... and she was gushing blood down her arm."

Meixner, who described the suspect as "really shy," said he "always kept to himself."

"He didn't talk to many people," she said. "He wasn't mean or anything, he just wasn't outgoing."

Mexiner said the suspect did not appear to be targeting anyone in particular..

Sophomore Cameron Lazor said he came upon students screaming and fighting at the intersection of two hallways, then noticed to his horror that "people were bleeding." Then, he said, the suspect ran off down the hall.

"I saw that he was carrying two knives that were the big knives you find in your kitchen," Lazor told USA TODAY. "He wasn't saying anything. He started running and that's when we saw our classmates bleeding.

"At first we just thought it was a group of boys being immature and fighting," he said. "We looked around, saw the blood and it was scary."

Nicole Damico, a junior at the school, told USA TODAY she and a friend were at their lockers when the alarm went off. They then heard the principal on a walkie-talkie shouting for more ambulances.

"We saw two kids down the hall and it looked like they were play-fighting," she said. "I realized that one had a knife so we sprinted out of the school. One of my peers had blood everywhere and he asked me for help. I just froze and ran out of the school. After that there was chaos."

Damico said students on social media were getting threatened last night that they would be beaten or killed.

"Us kids have been through hell and back. It made me realize that anything could happen at anytime. It was just a regular day," she said.

All of the victims were students, ages 14 to 17. At least eight people were hospitalized with serious injuries, said Mark Rubino of Forbes Hospital.

He said three students underwent surgery, and that five were being evaluated and that some of them may require surgery.

He said many of the victims have "deep penetrating injuries" to the lower abdomen and right flank.

Rubino said a 15-year-old girl applied pressure to the abdomen of one of the victims to stop the bleeding until medics arrived.

"We're sure that played a role in his ability to be treated," Rubino said.